1. Field of the Invention
The present invention relates to an explosive composition, in particular to an emulsion explosive composition suitable for loading pneumatically into a blasthole.
2. Description of the Related Art
Water-in-oil emulsion explosive compositions were first disclosed by Bluhm in U.S. Pat. No. 3,447,978 and comprise (a) a discontinuous aqueous phase comprising discrete droplets of an aqueous solution of inorganic oxygen-releasing salts; (b) a continuous water-immiscible organic phase throughout which the droplets are dispersed and (c) an emulsifier which forms an emulsion of the droplets of oxidiser salt solution throughout the continuous organic phase. Where these types of emulsions comprise very little water or adventitious water only in the discontinuous phase they are more correctly referred to as melt-in-fuel emulsion explosives.
Water-in-oil emulsion explosive compositions are generally viscous and require pumping and or auguring into a blasthole. Pumping and auguring equipment is generally expensive and the use of emulsion explosives in certain applications is limited because of the availability of such equipment at a cost effective price. Pumping of emulsion explosives is also generally undesirable due to the risk of accidental explosion due to heat or pressure build-up arising from a failure in the pumping mechanism.
ANFO-based explosive compositions may be pneumatically loaded into a blasthole. Compressed air is used to blow ANFO-based explosive compositions into a variety of blastholes including upholes. Even the so called “heavy ANFO” compositions which include a small amount of emulsion explosive blended with the ANFO are capable of being blow loaded. However, emulsion explosive compositions are themselves not generally suited for blow loading.
Pneumatic loading of emulsion explosive compositions has been proposed in, for example, British patent specification 2204343 and International patent application WO 97/48966. However, in both these proposals means is required to form a lubricating layer between the emulsion explosive composition, or the base emulsion phase, and the interior of a delivery hose.